Apparatus and process for the manufacture of paper



Dec. 11, 1962 w- E GOULD 3,067,816

APPARATUS AND PROCESS FOR THE MANUFACTURE OF PAPER Filed Jan. 20, 1960INVENTOR. Will/am E. Gould H/S ATTORNEY United States Patent G 3,067,816APPARATUS AND PROCESS FOR THE MANUFACTURE OF PAPER William E. Gould,Lewiston, N.Y., assignor to The Carborundum Company, Niagara Fails,N.Y., a corporation of Delaware Filed Jan. 20, 1960, Ser. No. 3,688 8Claims. (Cl. 162-374) This invention relates to an apparatus `andprocess for the manufacture of paper. More particularly, it relates toan improved suction box having a cover in which at least the outersurface thereof is composed of a dense, hard ceramic material and aprocess of making paper therewith.

ln order to produce paper, economically, high-speed machines operatingat peak eiciency must be used. The principal'tonnage of paper producedis processed on Fourdrinier machines. At the beginning of the century,the maximum speed at which these machines operated was in theneighborhood of 500 feet per minute. Today, speeds as high as 2,000 feetper minute are common. These increased speeds have substantiallydecreased the cost of producing paper. Yet, full advantage of thispotential has not been possible since the useful life of parts of themachines is materially limited by use at such high speeds.

In a Fourdrinier machine, a slurry of wood pulp and water is fed onto arapidly moving, endless wire screen. The slurry deposited on the screengenerally contains less than 1% wood pulp. The screen provides supportfor the libers While the iibers are matted'and the water drained olf. Asidewise shaking motion is imparted to the moving screen to help orientthe fibers and give better felting action. A large portion ofthe Waterwill normally drain through the` screen. To increase the speed andefficiency of the drainage, the wire passes over a series of suctionboxes. These are generally made of metal and have perforated coverswhicharein Contact =with the wire screen. A vacuum, which i'smaintained'in the suction boxes draws water from the partially feltedsheet into the boxes through the perforations in the cover. The waterwhich is withdrawn may be recirculated unless too strong- 1y colored.

Suction box covers used today are generally made of end grain maplewood. vAlthough the useful life of the covers themselves is adequate,they materially limit the useful life of the wire screen. The slurrypassing over the suction box covers on the wire screen invariably hasparticles of grit and dirt therein. Some of these particles becomeembedded in Ithe soft wood cover which results in an abrasive action onthe rapidly moving wire screen. The covers wear unevenly which alsocauses undue wear on the wire screen.

At present, the' industry obtainsV in the order of three to tive dayslife from wire-screens used on the large, high-speed machines. Suchscreens cost between $3,000 and $5,000 each. In addition to this cost,an extra shift of men is frequently required to change the screen and,of course, use of the machine must be discontinued. The substantialsavings involved in anyincrease of the useful life of a wire screen isreadily apparent. Even if the useful life of a wire screen could beincreased to six days, the savings would be very substantial. Not onlywould the number of screens used be reduced, but also the screen changescould be made on the weekend, thereby eliminating shutdowns during theworking week.

Several alternatives to the normal end grain maple box covers have beentested. Various plastics, rubbers and leather have proved unsuccessfulor not fully satisfactory. In general, covers made of these materialshave been too soft, wearing the wire rapidly due to the high friction3,067,816 Patented Dec. 11, 1952 "ice generated between covers of thesematerials and the wire screen. They pick up grit and other foreignmatter which abrades the wire screen. Dimensional stability has alsobeen a problem. For example, nylon has a low coefficient of frictionsuitable for use as a suction box cover, but it grows or expands dueevidently to water absorption.

My invention provides a suction box having a cover which will permitappreciably longer usage of the wire screens. I have found that suctionbox covers made of hard, dense, ceramic materials will not retain gritand other foreign particles which cause abrading action on the Wirescreen. Such covers are dimensionally stable and the coefiicient offriction between the cover and the wire screen is low. Furthermore, theuseful life of a cover made according to lmy invention is much longerthan the life of the wooden suction box covers now used.

In the drawings, FIGURE 1 is a perspective View illus- Y trating thegeneral arrangement of a paper-making machine in which my suction boxcover may be used;

FIGURE 2 is a plan view of a suction box having a cover made accordingto my invention attached thereto;

FIGURE 3 is a section taken on line III-III of FIG- i URE 2; and

FIGURE 4 is a sectional view of an alternative form of cover madeaccording to my invention.

Referring to FIGURE l, a slurry 10 of wood pulp and Water is fed from aflow box 11 onto a rapidly moving, endless wire screen 12. The screenpasses around end rolls 13, at least one of which is driven. The slurry,supported by the wire screen, passes o-ver table rolls 14 and suctionboxes 15. Normal drainage and a vacuum maintained in the suction boxesdraws orf a large portion of the water. The matted tibers are thenpassed to drying rolls and sheet rolling equipment, designated generallyat 16.

Suction boxes are composed of a wire-contacting cover 20 and a basemember 21. Each suction box is connectedto a vacuum source by means suchas suction lines 22. The covers 20 are provided with a plurality ofopenings or perforations 23 whereby the Vacuum maintained in the boxdraws -water from the partially felted fibers. Generally, each cover ismade of a plurality of segments 24, as shown in FIGURE 2.

Atleast the wire-contacting surfaces of suction box covers madeaccording to my invention are composed of a hard, dense ceramicmaterial. I prefer to use an impermeable ceramic having a density ofapproximately 8O percent or more of its theoretical density and ahardness of seven or more on Mohs scale.

Such materials `may be a self-bonded ceramic, such as high-densitself-bonded silicon carbide. It may be a ceramic-bonded ceramic, such assilicon nitride-bonded silicon carbide. Also suitable are the hard,dense, metalbonded ceramics, such as chromium-bonded alumina, and hard,dense impregnated ceramics, such as zirconiumV diboride impregnated withmolybdenum disilicide. Other specific hard,v dense ceramics which can beused include titanium carbide, boron carbide, tungsten carbide,zirconium carbide, titanium boride, zirconium boride, titanium nitride,zirconia, alumina, nitride-bonded silicon carbide, metal-bonded titaniumcarbide, and metal-bonded tungsten carbide.

The manufacture of hard, dense ceramics is known to the art. Forexample, Schildhauer et al. U.S. Patent No. 2,907,972 discloses themanufacture of dense silicon car. bide. The preparation ofchromium-bonded alumina is disclosed in Conant et al. U.S. Patent No.2,698,990. The suction box cover may be formed with the openings orperforations 23 therein by standard ceramic forming techniques. Thedynamic bearing surfaces should be smooth and are, therefore diamondground, if necessary.

As shown in FIGURE 3, suction box covers may be made entirely of thehard, dense ceramic material or,

as shown in FIGURE 4, a wire-contacting ceramic section may be bonded toa base plate 31. Also, a layer of hard, dense ceramic could be coated orsprayed on a base plate. Any common material such as steel may be usedfor the base plate. Preferably, it should be capable of receiving screwsor other fastening means directly from the base of the box. Epoxy resinswill form a good bond between the ceramic section and the base plate. Ifa solid ceramic cover is used, clamping means, such as shown in FIGURE3, are preferable to direct connection between the box base 21 and thecover 20. I have shown a fixed clamp 3S fastened to one side of the boxbase and a movable clamp 36 mounted on the opposed side of the box base.

While the initial cost of suction boxes made according to my inventionis greater than that of suction boxes with maple covers presently used,it is readily apparent that the cost of operating a machine having mysuction boxes will he substantially less than one using boxes having thecommon wood covers. In a test on an operating Fourdrinier iachine, onesegment in each of eight suction box covers was made of hard, dense,self-bonded silicon carbide. The remaining segments were end grainmaple. The sections of the wire screens which contacted only the ceramicsegments showed approximately 30 to 40 percent less wear than thesections of the same wire screens which contacted the end grain maplesegments. Furthermore, after three-months operation, the ceramicsegments showed practically no wear, whereas the maple segments showedextensive wear. Thus, it is apparent that by use of my invention, theuseful lives of 4wire screens and suction box covers are substantiallyincreased. Maintenance costs are materially reduced and the powerrequired to operate the machine is likewise reduced.

While I have described the present preferred embodiments of myinvention, it is to be understood that it may be otherwise embodiedwithin the scope of the following claims.

I claim:

l. A suction box cover for a paper-making machine including a movingWire screen, said cover comprising a screen contacting surface portionthat is dense, hard, and wear-resistant and that will not retain gritand other foreign particles which cause abrading action on said screen,said surface portion being composed of an impermeable ceramic materialhaving a hardness of at least 7 on Mohs scale.

2. In paper-making machines in which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover contacting the moving wire screenand having a dense, hard, wear-resistant, wire contacting surface thatwill not retain grit and other foreign particles which cause abradingaction on said screen, said cover being composed of an impermeableceramic material having a hardness of at least 7 on Mohs scale.

3. In paper-making machines in which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover comprising a base plate and awirecontacting section bonded to said base plate, said section having awire-contacting surface that is dense, hard, and wear-resistant and thatwill not retain grit and other foreign particles which cause abradingaction on said screen and said wire-contacting section being composed ofan impermeable ceramic material having a hardness of at least 7 on Mohsscale.

4. In paper-makingrmachinesin which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover comprising a plurality ofperforated, wire-contacting segments each having a dense, hard,wear-resistant surface that will not retain grit and other foreignparticles which cause abrading action on said screen and saidwire-contacting segments consisting essentially of an impermeableceramic material having a hardness of at least 7 on Mohs scale.

5. A suction box cover for a paper-making machine including a movingwire screen, said cover comprising a screen contacting surface portionthat is dense, hard, and wear-resistant and that will not retain gritand other foreign particles which cause abrading action on said screen,said surface portion being composed of an impermeable ceramicY materialof the character of self-bonded silicon carbide, and having a density ofat least percent of its theoretical density and a hardness of at least 7on Mohs scale.

6. In paper-making machines in which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover contacting the moving wire screenand having a dense, hard, wear-resistant, wire contacting surface thatwill not retain grit and other foreign particles which cause abradingaction on said screen, said cover being composed of self-bonded siliconcarbide, and having a density of at least 80 percent of its theoreticaldensity and a hardness of at least 7 on Mohs scale.

7. In paper-making machines in which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover comprising a base plate and awirecontacting section bonded to said base plate, said section having awire-contacting surface that is dense, hard, and wear-resistant and thatwill not retain grit and other foreign particles which cause abradingaction on said screen and said Wire-contacting section being composed ofself-bonded silicon carbide, and having a density of at least 80 percentof its theoretical density and a hardness of at least 7 on Mohs scale.

8. In paper-making machines in which a moving wirescreen member passesover and contacts a suction box, an improved suction box comprising: abase member and a cover, said cover comprising a plurality ofperforated, wire-contacting segments each having a dense, hard,wearresistant surface that will not retain grit and other foreignparticles which cause abrading action on said screen and saidywire-contacting segments consisting essentially of selfbonded siliconcarbide, and having a density of at least 80 percent of its theoreticaldensity and a hardness of at least 7 on Mohs scale.

References Cited in the le of this patent UNITED STATES PATENTS 128,469Curtis Iuly 2, 1872 1,644,867 Berry Oct. 11, 1927 1,703,010 Manson Feb.19, 1929 2,215,572 Wilson Sept. 24, 1940 2,602,714 Wheildon July 8, 19522,637,091 Nicholson May 5, 1953 FOREIGN PATENTS 770,832 Great BritainJune 15, 1955

